1. Field of the Invention
The present invention relates to an induction heating cooking apparatus. More specifically, the present invention relates to an induction heating apparatus capable of temperature control operation wherein the state of heating a foodstuff to be cooked in a cooking pan is controlled.
2. Description of the Prior Arts
The induction heating cooking apparatus, as is well known, generates a high frequency current by an inverter and produces a high frequency alternative magnetic field from a heating coil by this high frequency current. Above this heating coil, a cooking pan made of an iron group metal is closely disposed through a top plate composed of, for instance, ceramics or the like. This cooking pan is heated by a current induced by the high frequency alternating magnetic field. In such an induction heating cooking apparatus, the state of heating, that is, the power of inverter is controlled in response to the temperature of the foodstuff to be cooked in the cooking pan.
For instance, in Japanese Utility Model Publication Gazette No. 53036/1983 published for opposition on Dec. 2, 1983, an induction heating cooking apparatus is disclosed wherein a thermo-sensitive device is installed directly beneath the top plate, and thereby the temperature of the cooking pan is detected directly, in the prior art the temperature of the foodstuff can not be detected directly, and accordingly, this has a disadvantage of not-so-good precision.
Furthermore, in U.S. Pat. No. 3,742,174 patented on June 26, 1973 an induction heating cooking apparatus is disclosed wherein a thermistor and a light emitting diode which generates a light in response to the output of the thermistor are built-in at the bottom part of the cooking pan, and the light from the light emitting diode is detected in the cooker main unit through the top plate, and thereby the temperature operation is performed. In the induction heating cooking apparatus as disclosed in this prior patent, no ordinary cooking pan can be used, and also the top plate is required to be made of a light transmitting material. However, materials having a light transmitting property, heat resisting property and sufficient mechanical strength are expensive, and accordingly, the cooker itself becomes expensive.
Furthermore, in U.S. Pat. No. 3,742,175 patented on June 26, 1973, an induction heating cooking apparatus is disclosed which detects the temperature of a foodstuff to be cooked. using a temperature measuring probe, and the power can be controlled in response to the measured temperature. Use of the temperature measuring probe allows a direct detection of the temperature of the foodstuff to be cooked, therefore being more advantageous compared with the two prior arts as cited previously. However, in this prior art patent, an induction system is employed to transmit the signal outputted from the temperature measuring probe into the cooker main unit. As is described above in the induction heating cooking apparatus, however, a high frequency current, that is, a high frequency alternating magnetic field is produced, and therefore this magnetic field affects the transmitting path of the signal from the temperature measuring probe, and accordingly there is a possibility of misoperation.